1. Field of the Invention
This invention relates to a method of and apparatus for reducing the emitted amount of particulates contained in the exhaust gas of a diesel engine, wherein the particulates such as carbon particles and the like contained in the exhaust gas are collected by a trapper provided in an exhaust system of the diesel engine to thereby clean the exhaust gas.
2. Description of the Prior Art
Although the diesel engines have a low fuel consumption rate in general, an emitted amount of the particulates that are products due to incomplete combustion in the exhaust gas is high, and hence, it is necessary to emit the exhaust gas in a condition where the aforesaid particulates have been eliminated.
There has heretofore be known such a method that a trapper having, as its principal element, a trapping member consisting of a porous material is mounted in an exhaust system of a diesel engine, whereby the particulates are caused to adhere to the trapping member to be caught therein. In the conventional method of collecting the particulates of the type described, the pressure loss of the exhaust gas in the exhaust system increases along with the increase in amount of the particulates which have adhered to the trapping member, thus resulting in decreased output of the diesel engine. Consequently, it is required to replace or regenerate the trapper every running distance of several hundred kilometers. However, the trapper is preferably regenerated because the replacement of the trapper is uneconomical.
Heretofore, there has been commonly practised such a trapper regenerating method that an auxiliary burner including an air-fuel blowing nozzle and igniting means is operated whenever necessary to burn the particulates which have adhered to the trapping member. In other words, this is a method in which the particulates which have adhered to the trapping member are completely burned to be gasified. However, the particulates are hard to be ignited and burned, and, even when the secondary air is introduced for propagating combustion by use of the auxiliary burner, about 10 minutes are required to regenerate a trapper having a length of 100 (mm). Moreover, this method requires a large supply of fuel for the operation of the auxiliary burner, thereby reducing a merit in fuel consumption rate to be obtained in diesel engines. Further, it is not desirable to mount the auxiliary burner in the exhaust system as in this method.